This invention relates to spread-coating compositions for improving the surface properties of paper, which comprises an aqueous dispersion of a styrene/butadiene-polymer as a synthetic binder, polyethylene oxides, pigments, optical brighteners, fillers and other customary auxiliary agents.
Paper spread-coating agents are utilized in technical applications to improve the surface properties of paper. The binder used in these spread-coating compositions frequently has two components, viz., a synthetic emulsion polymer and a naturally-occurring binder, e.g., pearl starch, soybean protein, casein. The naturally-occurring binders employed have the disadvantages that they are often not readily available and are non-uniform in quality. Therefore, efforts have been made in the art to develop spread-coating compositions containing synthetic binders exclusively.
Paper spread-coating agents based on synthetic binders have a number of disadvantages. For example, addition of synthetic binders adversely affects the behavior of optical brighteners and the water retention properties of the resultant coatings.
It is an object of the present invention to provide an additive for paper spread-coating compositions which makes possible the production of satisfactory spread-coating compositions without requiring the use of naturally-occurring binders. It is a further object of this invention to produce overall properties as good as those obtained by using natural binders.